A new pressure plate extractor, referred to as the leak-free pressure plate extractor (LFPPE), is described where air leakage around the ceramic plate effectively is eliminated. The LFPPE was designed so that it would be robust, easy to use, and readily assembled and disassembled for testing and maintenance. An example shows that the LFPPE yields a soil water characteristic curve (SWCC) that is consistent with portions of the SWCC measured with other independent methods (chilled mirror hygrometer and hanging column). A testing procedure is also described that has been employed for measuring numerous SWCCs with the LFPPE without an incident of air leakage.